Conventionally, a bearing ring for use in a rolling bearing and divided into two with respect to the circumferential direction to facilitate assembling and attachment in manufacturing is know as a split bearing ring. In general, such split bearing rings are manufactured by heat-treating an annular bearing ring, dividing it into two by cracking, recombining them together, and grind-finishing the raceway surfaces.
Various methods for dividing a bearing ring by cracking have conventionally been proposed. For example, as a method for causing a split between slits formed at both axial ends of a bearing ring, it has been proposed to form stress concentration points such as V-grooves or inducing holes in the bearing ring in advance so that the shape of the split line is controlled to be in a desired shape such as an S shape (see, e.g., Patent Documents 1-3). Also, it has been proposed to split a bearing ring so as to form a split line that is inclined with respect to the axial direction, thereby improving the adhesion between split faces (see, e.g., Patent Documents 4-7).
Further, to prevent a situation where split lines do not meet each other when cracking from both sides in the axial direction, it has been proposed to open from a slit formed on one end side in the axial direction (see, e.g., Patent document 8).
Further, in forcibly breaking and separating (cracking) a low-ductility microalloyed hot forging steel, it has been proposed to make the surface roughness Rz of fracture faces to be 30 μm to 1,000 μm to enable an easy positioning after the splitting (see, e.g., Patent document 9).